Does my connection have IPv6?
Your browser asks a host that only has an IPv4 address and one that only has an IPv6 address. Whichever answers shows the address websites see over that protocol.
This page arrived over IPv…
Checking…
Each family is checked against a host that only speaks it.
IPv4…
IPv6…
Short answer
Most home and mobile networks now hand out both. When both work, your browser usually prefers IPv6 (RFC 8305, “Happy Eyeballs”), so sites can see a different address, and sometimes a different location, than an IPv4-only check shows.
Why your two addresses can disagree
Location databases track IPv4 and IPv6 ranges separately, and IPv6 coverage is often thinner, so the same connection can be placed in two different cities. A VPN that only tunnels IPv4 leaves IPv6 traffic going out directly, which the VPN check flags as an IPv6 leak.